Field of the Invention
The present invention relates to the field of wireless power generation and more particularly to managing power distribution in a wireless environment.
Description of the Related Art
Modern society is dependent on power and, thus, on electricity. One no longer burns a candle for the illumination required to read a book at night, but instead one expects to have light to read by when flipping on a light switch. Almost every device of daily life requires power—a coffee pot, an alarm clock, a television. To access the power required to use the device, one generally connects the device to a power outlet using a cord. Oftentimes, however, there are more devices requiring power outlets then there are accessible power outlets. In consequence, in many cases one must choose between devices to power with an available power outlet and devices to remain unpowered. The problem of limited power outlets can be compounded in a public environment, where there are often no power outlets available to the public. Power splitters provide additional power outlets by augmenting a single power outlet into two or more power outlets, but power cords of different devices easily can become tangled. In addition, overloading power splitters causes electrical fires and is not permitted by the fire code of many municipalities.
More recently, devices, such as portable computers (laptops) and mobile telephones, no longer require a power cord be plugged in to a wall outlet to function, but still require power to work. These devices often function from battery power, but if the battery power becomes fully drained the device no longer can function and will shut down. Depending on what device is in use, the loss of power can cause one to lose important data or documents. Once a battery becomes low in charge or completely drained, the battery can be recharged, but one still must use a power cord attached to the device and connected to a wall outlet to charge the battery; thus, one still must carry the power cord and have access to a power outlet.
To address the difficulties of tethering a device to a power outlet in order to derive power for the device, wireless power distribution networks have been deployed in selective environments. Wireless energy transfer or wireless power distribution refers to the transmission of electrical energy from a power source to an electrical load without interconnecting wires. Wireless power differs from wireless telecommunications, where the signal-to-noise ratio (SNR) or the percentage of energy received becomes critical only if it is too low for the signal to be adequately recovered. With wireless power transmission, efficiency is the more important parameter. The most common form of wireless power transmission is carried out using inductive coupling followed by resonant inductive coupling. Other methods include microwaves and lasers.
Electromagnetic induction wireless transmission techniques are near field over distances comparable to a few times the diameter of the device or devices approaching one quarter of the wavelength used. Near field energy itself is non-radiative but some radiative losses do occur. In addition there are usually resistive losses. Energy transfer by induction is usually magnetic but capacitive coupling can also be achieved. Electromagnetic induction find recent application to the wireless inductive charging of batteries. Inductive charging uses the electromagnetic field to transfer energy between two objects. Specifically, a charging station sends energy through inductive coupling to an electrical device, which stores the energy in the batteries.